The present invention is related to a charging generator controller for vehicles, especially vehicles to be driven appropriately by an engine with large variation of load.
Every car has a battery and a battery charging generator to supply power to the electric loads such as lamps, actuators, and so on. In general, the generator is controlled so that the rotating magnetic field coil is excited by the rotating force of the drive torque generated by the engine, and the battery voltage generated in the field coil by the rotating magnetic field i maintained at a specified value.
However, when the electric load becomes large, due, for example to a lamp switch being turned on, the power output of the generator must also be increased. To meet this requirement, the generator is controlled so that the current flowing in the field .coil may increase sharply when the electric load becomes large. As a result, the power output of the generator increases, the driving torque becomes large and the balance between the driving torque and engine torque is lost. The engine speed therefore drops until the engine torque equals that required to drive the generator. In the worst case, the engine may stall. Especially in the idling state, a rapid torque change, which is greater than the response speed of the engine rotation control, will become a problem, because the engine speed is controlled at a fixed value, assuming that the balance between the engine and driving torques of auxiliary devices including the generator is maintained.
To suppress such phenomenon, a control method has been considered to reduce the rapid rise of the current flowing in the field coil, and thus minimize the sudden change of the generator torque for the engine when the electric load suddenly increases. This type of control, referred to as Load Responsive Control, is described in Japanese Patent laid open No. 60-27280. The control technology to suppress the sudden rise of the current flowing in a field coil when the continuity rate of the switch elements connected serially to the field coil increases more than the specified value is also given in Japanese Laid-Open Patent No. 60338/1991.
In the conventional technology described above, the control apparatus is configured so that the continuity rate of the switch elements is detected, and minor loop control is always actuated to delay the increasing flow of field current in the field coil. This operation is continued even in the steady state in which the engine speed and the output current are stable. However, although the rate of increase in the flow of magnetic field current is slower, the rate of decrease remains equal to that of the conventional circuit without minor loop control.
Similarly, the surge of the output voltage caused by the rapid rise of the field current also becomes slower, but the rate of decrease in voltage remains equal to that of the conventional circuit without minor loop control. The average value of output voltage with no minor loop control is almost equal to the center value of the output voltage surge. In contrast, with minor loop control the average output voltage goes below the center value of the output voltage surge. With the effects mentioned above, the voltage decrease characteristics in which the output voltage decreases as the output current increases becomes much larger than that of the conventional circuit without minor loop control, causing the charging/discharging balance of vehicles to be degraded.
An object of the present invention is to provide a charging generator control for vehicles, which allows the magnetic field current to respond immediately to the output voltage, and thus to control the output voltage precisely.
Another object of the present invention is to provide a charging generator control for vehicles, in which the integrating circuit used for load corresponding control in the steady state (that is, when the output current is stable, or when a small electric load is applied) does not affect the voltage control loop at all.